Technical Abstract:
Within the layer industry, commercially available attenuated strains of Mycoplasma gallisepticum (MG) are commonly used to control MG-induced mycoplasmosis. Strain 6/85 is a commonly utilized vaccine strain which has been demonstrated to be safe due to reduced pathogenicity and transmissibility. To further examine the protection afforded by 6/85, the persistence of the strain was monitored in 120 commercial layer chickens housed in biological isolation units (10 layer hens/unit) divided among 3 treatment groups: (1) commercial layer hens vaccinated with 6/85 at 10 wks of age (n=40); (2) commercial layer hens vaccinated with 6/85 at 10 wks of age and challenged with the F strain of MG (FMG) at 22 wks of age (n=40); and commercial layer hens vaccinated with 6/85 at 10 wks of age and challenged with FMG at 45 wks of age (n=40). The in vivo persistence of 6/85 was determined via culturing swabs of the choanal cleft and subsequent MG-specific pvpA PCR. Sampling included preliminary random sampling of 25% of the layer hens of each treatment group at 48 wks of age and subsequent sampling of all study participants at 59 wks of age. Preliminary results demonstrated 6/85 survivability in 10%, 30%, and 10% of layer hens vaccinated with 6/85 at 10 wks singly, layer hens vaccinated with 6/85 at 10 wks of age and FMG at 22 wks of age, and layer hens vaccinated with 6/85 at 10 wks of age and FMG at 45 wks of age, respectively.